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Aerospace, Volume 9, Issue 12 (December 2022) – 113 articles

Cover Story (view full-size image): This paper proposes a distributed turbo-electric hybrid propulsion system architecture for air–ground aircraft, consisting mainly of the turboshaft engine, hybrid energy storage unit and distributed electric drive-propulsion units. Power calculation, energy and weight analysis are conducted under the air–ground amphibious profile. Genetic algorithm is applied to sizing for optimal total weight and propulsion efficiency, and the energy management framework is designed by adopting an equivalent consumption minimum strategy and fuzzy logic control. Simulation results indicate that this architecture can achieve a 21.80% fuel consumption and CO2 emission optimization rate at the cost of 10.53% mass increase compared to the oil-powered system. Hybrid energy storage can reduce mass by 8.1% and volume by 3.77% compared to the single storage. View this paper
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24 pages, 12441 KiB  
Article
Aeroservoelastic Stability Evaluation for Slender Vehicles Based on the Ground Frequency Response Test
by Changkun Yu, Zhigang Wu and Chao Yang
Aerospace 2022, 9(12), 850; https://doi.org/10.3390/aerospace9120850 - 19 Dec 2022
Cited by 1 | Viewed by 1876
Abstract
With the increasing bandwidths of servo control systems and decreasing mode frequencies, aeroservoelastic (ASE) stability evaluation has become an essential part of flight vehicle design. However, the theoretical method is limited by the modeling errors of numerical models, and the dry wind tunnel [...] Read more.
With the increasing bandwidths of servo control systems and decreasing mode frequencies, aeroservoelastic (ASE) stability evaluation has become an essential part of flight vehicle design. However, the theoretical method is limited by the modeling errors of numerical models, and the dry wind tunnel method is limited by the complex design of force controllers. Given these limitations, a novel ASE stability evaluation method for slender vehicles based on the ground frequency response test (FRT) is proposed in this paper. FRTs are implemented for a slender vehicle to obtain the frequency response functions (FRFs) of the real structure and servo control systems. The low-order unsteady aerodynamic FRFs established in physical coordinates are calculated by the quasi-steady aerodynamic derivative method. An ASE open-loop FRF is established for stability evaluation via the Nyquist criterion. Comparison with the theoretical results shows that the proposed method is feasible and accurate for different positions of the inertial measurement unit, different control laws, and different Mach numbers. To deal with the unavoidable influence of hanging supports in the test, an FRF fitting and resynthesis method is used to remove the hanging modes and provide an accurate ASE open-loop FRF with free–free boundary conditions. Full article
(This article belongs to the Section Aeronautics)
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15 pages, 5377 KiB  
Article
Development of a Complex Mathematical and Hardware-in-the-Loop Simulation of the System for Controlling the Skew of Sections of Mechanization of the Wing
by Aleksandr Chibizov, Marina Podzharskaya and Alexey Trofimov
Aerospace 2022, 9(12), 849; https://doi.org/10.3390/aerospace9120849 - 19 Dec 2022
Viewed by 1830
Abstract
In this paper, an innovative approach to the development of a skew control system is discussed to increase the speed and quality of the development of this system. To achieve this goal, we chose the Hardware-in-the-Loop simulation method, which involved creating a mathematical [...] Read more.
In this paper, an innovative approach to the development of a skew control system is discussed to increase the speed and quality of the development of this system. To achieve this goal, we chose the Hardware-in-the-Loop simulation method, which involved creating a mathematical model to test a real control unit. This method reduced time and material costs at both the development and testing stages by enabling quick reconfiguration of the system and the changing parameters of the control model. As a result of this work, we developed a complex of mathematical and full-scale simulations, which included the SCS simulation scheme with distortion detection algorithms and SCS semi-random simulation stand. Full article
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21 pages, 5496 KiB  
Article
A Novel Strategic Aircraft Track Planning Method Considering Conflict Probability
by Ruiwei Liu, Siqi Hao, Yaping Zhang, Chonghang Xu, Wenjing Li and Yunrui Mo
Aerospace 2022, 9(12), 848; https://doi.org/10.3390/aerospace9120848 - 19 Dec 2022
Viewed by 1852
Abstract
Generally, air track planning is conducted in real time and takes modified track distance minimization as objective. Next-generation air transport systems provide aircrafts with more flexibility in track planning and more responsibilities in self-separation, which present a great challenge for aircraft optimal track [...] Read more.
Generally, air track planning is conducted in real time and takes modified track distance minimization as objective. Next-generation air transport systems provide aircrafts with more flexibility in track planning and more responsibilities in self-separation, which present a great challenge for aircraft optimal track planning, especially in some high-density airspaces and some complex conflict scenarios. This paper proposes a novel aircraft track planning method by taking aircraft conflict probability into consideration. First, the concepts of aircraft potential motion space and the estimation method for aircraft conflict probability is introduced. Then, taking conflict probability minimization as the objective, the classical ant colony algorithm (ACA) algorithm is improved to solve the model. Finally, an experimental study is conducted to illustrate the proposed method. Results show that the proposed method is able to provide a scientific and effective track planning approach considering the potential conflict probability of aircrafts, which is able to provide fundamental to the safety of entire air transport system. Full article
(This article belongs to the Section Air Traffic and Transportation)
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24 pages, 5875 KiB  
Article
Improving Algorithm Conflict Resolution Manoeuvres with Reinforcement Learning
by Marta Ribeiro, Joost Ellerbroek and Jacco Hoekstra
Aerospace 2022, 9(12), 847; https://doi.org/10.3390/aerospace9120847 - 19 Dec 2022
Cited by 3 | Viewed by 2428
Abstract
Future high traffic densities with drone operations are expected to exceed the number of aircraft that current air traffic control procedures can control simultaneously. Despite extensive research on geometric CR methods, at higher densities, their performance is hindered by the unpredictable emergent behaviour [...] Read more.
Future high traffic densities with drone operations are expected to exceed the number of aircraft that current air traffic control procedures can control simultaneously. Despite extensive research on geometric CR methods, at higher densities, their performance is hindered by the unpredictable emergent behaviour from surrounding aircraft. In response, research has shifted its attention to creating automated tools capable of generating conflict resolution (CR) actions adapted to the environment and not limited by man-made rules. Several works employing reinforcement learning (RL) methods for conflict resolution have been published recently. Although proving that they have potential, at their current development, the results of the practical implementation of these methods do not reach their expected theoretical performance. Consequently, RL applications cannot yet match the efficacy of geometric CR methods. Nevertheless, these applications can improve the set of rules that geometrical CR methods use to generate a CR manoeuvre. This work employs an RL method responsible for deciding the parameters that a geometric CR method uses to generate the CR manoeuvre for each conflict situation. The results show that this hybrid approach, combining the strengths of geometric CR and RL methods, reduces the total number of losses of minimum separation. Additionally, the large range of different optimal solutions found by the RL method shows that the rules of geometric CR method must be expanded, catering for different conflict geometries. Full article
(This article belongs to the Special Issue Application of Data Science to Aviation II)
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15 pages, 9394 KiB  
Article
Inlet Gap Influence on Low-Frequency Flow Unsteadiness in a Centrifugal Fan
by Martin Ottersten, Hua-Dong Yao and Lars Davidson
Aerospace 2022, 9(12), 846; https://doi.org/10.3390/aerospace9120846 - 19 Dec 2022
Cited by 4 | Viewed by 3109
Abstract
In this study, unsteady low-frequency characteristics in a voluteless low-speed centrifugal fan operating at a high mass flow rate are studied with improved delayed detached eddy simulation (IDDES). This study is motivated by a recent finding that the non-uniformly distributed pressure inside this [...] Read more.
In this study, unsteady low-frequency characteristics in a voluteless low-speed centrifugal fan operating at a high mass flow rate are studied with improved delayed detached eddy simulation (IDDES). This study is motivated by a recent finding that the non-uniformly distributed pressure inside this type of fan could be alleviated by improving the gap geometry. The present simulation results show that the velocity magnitudes of the gap have distinct low and high regions. Intensive turbulent structures are developed in the low-velocity regions and are swept downstream along the intersection between the blade and shroud, on the pressure side of the blade. Eventually, the turbulence gives rise to a high-pressure region near the blade’s trailing edge. This unsteady flow behavior revolves around the fan rotation axis. Additionally, its period is 5% of the fan rotation speed, based on the analysis of the time history of the gap velocity magnitudes and the evolution of the high-pressure region. The same frequency of high pressure was also found in previous experimental measurements. To the authors’ knowledge, this is the first time that the trigger of the gap turbulence, i.e., the unsteady local low velocity, has been determined. Full article
(This article belongs to the Special Issue Aeroacoustics and Noise Mitigation)
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17 pages, 7412 KiB  
Article
An Onboard Adaptive Model for Aero-Engine Performance Fast Estimation
by Zhen Jiang, Shubo Yang, Xi Wang and Yifu Long
Aerospace 2022, 9(12), 845; https://doi.org/10.3390/aerospace9120845 - 18 Dec 2022
Cited by 2 | Viewed by 1695
Abstract
The onboard adaptive model is essential to the model-based control and diagnosis of the engine. However, current methods, such as the Kalman-based and the data-driven ones, cannot meet the demands of performance estimation well. Their self-tuning processes lead to a long period of [...] Read more.
The onboard adaptive model is essential to the model-based control and diagnosis of the engine. However, current methods, such as the Kalman-based and the data-driven ones, cannot meet the demands of performance estimation well. Their self-tuning processes lead to a long period of model mismatch and, thus, degrade the quality of control and diagnosis, even causing engine failures. To overcome this disadvantage, a novel onboard adaptive model with fast estimation capability is proposed. The proposed method employs a component level model as the benchmark and introduces some scaling factors as the model tuners. These tuners are derived from the measurements and defined to quantify the characteristic deviations of the engine components at a certain operating condition. An algorithm with memory function is introduced to store the correlations between the tuners and the operating condition and, thus, predict these tuners according to the operating condition of inputs. By feeding the predicted tuners to the benchmark model, the engine performance can be estimated rapidly. Simulations are implemented to demonstrate the effectiveness of the proposed model. The results show that it has not only a high estimation accuracy at steady operating states, but also a short dynamic response time and the memory ability to avoid repeated self-tuning processes when the operating state of the engine varies. Full article
(This article belongs to the Section Aeronautics)
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11 pages, 5399 KiB  
Article
Contrast Icing Wind Tunnel Tests between Normal Droplets and Supercooled Large Droplets
by Zhirong Han, Jiangtao Si and Dawei Wu
Aerospace 2022, 9(12), 844; https://doi.org/10.3390/aerospace9120844 - 18 Dec 2022
Cited by 2 | Viewed by 2371
Abstract
In order to compare and analyze the similarities and differences between normal droplet icing shapes and supercooled large droplet icing shapes, SADRI carried out normal droplet and supercooled large droplet icing wind tunnel tests in the NRC−AIWT icing wind tunnel. Taking the typical [...] Read more.
In order to compare and analyze the similarities and differences between normal droplet icing shapes and supercooled large droplet icing shapes, SADRI carried out normal droplet and supercooled large droplet icing wind tunnel tests in the NRC−AIWT icing wind tunnel. Taking the typical glaze ice in normal droplet icing conditions as the reference, the freezing drizzle and freezing rain icing tests under the supercooled large droplet conditions were carried out. The test results show that compared with normal droplets, the ice horn height of supercooled large droplets decreases with the increase in droplet particle size, and even the ice horn characteristics are not obvious when the icing condition is freezing rain. At the same time, the range and height of rough element ice shape after the main ice horn of supercooled large droplets are significantly larger and higher than those of the normal droplets, while the difference in the rough element in different supercooled large droplet icing conditions is small. Full article
(This article belongs to the Special Issue Thermal Fluid Dynamics and Control in Aerospace)
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18 pages, 3115 KiB  
Article
Reverse Design of a Novel Coupling Strut for Vibration Attenuation in the Helicopter Cabin
by Ming Ding, Jinhui Jiang, Fang Zhang, Xiao Liang and Nansun Shen
Aerospace 2022, 9(12), 843; https://doi.org/10.3390/aerospace9120843 - 18 Dec 2022
Cited by 1 | Viewed by 1637
Abstract
Helicopter gearbox support strut is one of the main research objects in the field of vibration and noise control in helicopter cabins. Aiming to further widen the vibration attenuation range of traditional Bragg periodic struts, a novel type of Local resonance (LR)/Bragg coupling [...] Read more.
Helicopter gearbox support strut is one of the main research objects in the field of vibration and noise control in helicopter cabins. Aiming to further widen the vibration attenuation range of traditional Bragg periodic struts, a novel type of Local resonance (LR)/Bragg coupling periodic strut with graded parameters as well as the reverse design method is proposed. Combined with the spectral element method (SEM) and the transfer matrix method (TMM), the analytical expression of the transform relationship of longitudinal vibrations through the coupling strut is yielded. The impacts of different parameters on the boundaries of bandgaps are explored according to the results of simulation analysis. On this basis, the gradient of parameters is determined, and then all unknown structural parameters can also be determined. Compared with the traditional Bragg periodic struts and the LR/Bragg coupling periodic strut with non-graded parameters, the presented strut has an obvious advantage of widening the low-frequency bandgaps below 500 Hz. Full article
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21 pages, 2428 KiB  
Article
Trajectory Planning and Tracking for a Re-Entry Capsule with a Deployable Aero-Brake
by Egidio D’Amato, Immacolata Notaro, Giulia Panico, Luciano Blasi, Massimiliano Mattei and Alessia Nocerino
Aerospace 2022, 9(12), 841; https://doi.org/10.3390/aerospace9120841 - 18 Dec 2022
Cited by 9 | Viewed by 3126
Abstract
In the last decade, the increasing use of NanoSats and CubeSats has made the re-entry capsule an emerging research field needing updates in configuration and technology. In particular, the door to advancements in terms of efficiency and re-usability has been opened by the [...] Read more.
In the last decade, the increasing use of NanoSats and CubeSats has made the re-entry capsule an emerging research field needing updates in configuration and technology. In particular, the door to advancements in terms of efficiency and re-usability has been opened by the introduction of inflatable and/or deployable aerodynamic brakes and the use of on-board electronics for active control. Such technologies allow smaller sizes at launch, controlled re-entries, and safe recovery. This paper deals with the design of a guidance and control algorithm for the re-entry of a capsule with a deployable aero-brake. A trajectory optimization model is used both in the mission planning phase to design the reference re-entry path and during the mission to update the trajectory in case of major deviations from the prescribed orbit, thanks to simplifications aimed at reducing the computational burden. Successively, a trajectory tracking controller, based on Nonlinear Model Predictive Control (NMPC), is able to modulate the opening of the aero-brake in order to follow the planned trajectory towards the target. A robustness analysis was carried out, via numerical simulations, to verify the reliability of the proposed controller in the presence of model uncertainties, orbital perturbations, and measurement noise. Full article
(This article belongs to the Section Astronautics & Space Science)
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27 pages, 18836 KiB  
Article
Investigation of Improvement Design on Aileron Surface Flow State of High Lift Configuration in BWB
by Xiaotian Niu, Jie Li, Heng Zhang and Zhao Yang
Aerospace 2022, 9(12), 842; https://doi.org/10.3390/aerospace9120842 - 17 Dec 2022
Cited by 2 | Viewed by 3404
Abstract
The aileron is one of the most important tools for adjusting the roll attitude of the aircraft, but the surface flow state of the aileron is likely to be affected by high-lift devices. In this paper, by using computational fluid dynamics (CFD) simulations [...] Read more.
The aileron is one of the most important tools for adjusting the roll attitude of the aircraft, but the surface flow state of the aileron is likely to be affected by high-lift devices. In this paper, by using computational fluid dynamics (CFD) simulations and wind tunnel tests, the Krueger flap effects on the surface flow state of ailerons in a typical blended wing body civil aircraft were investigated. In order to increase the lift, deflecting the Krueger flap makes the flow separation occur on the aileron surface of BWB civil aircraft. This way of the surface stall that the flow separation in the aileron zone first appears at the wing tip rather than at the wing root is unreasonable for civil aircraft. For the above problem, a sensitivity analysis of the design parameters of the Krueger flaps was carried out. The results indicate that the angle of the outboard Krueger flap mainly affects the flow separation of the ailerons. Its length affects the pitch moment tremendously, while its width slot affects the pitch moment slightly. Finally, the design principles of the BWB Krueger flap for the improvement aileron surface flow state were proposed, and the redesign of the BWB high lift configuration significantly improved the flow state of the aileron zone at a minimal cost of aerodynamic characteristics without losing the existing great aerodynamic performance. Full article
(This article belongs to the Special Issue Aerodynamics Design)
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21 pages, 907 KiB  
Article
Constrained Integrated Guidance and Control Scheme for Strap-Down Hypersonic Flight Vehicles with Partial Measurement and Unmatched Uncertainties
by Minzhou Dong, Xinkai Xu and Feng Xie
Aerospace 2022, 9(12), 840; https://doi.org/10.3390/aerospace9120840 - 17 Dec 2022
Cited by 6 | Viewed by 1663
Abstract
This paper investigates the issue of integrated guidance and control (IGC) design for strap-down hypersonic flight vehicles with partial measurement information and unmatched uncertainties. A constrained IGC scheme is proposed by combining the barrier Lyapunov function-based backstepping methodology and the specific output-based finite-time [...] Read more.
This paper investigates the issue of integrated guidance and control (IGC) design for strap-down hypersonic flight vehicles with partial measurement information and unmatched uncertainties. A constrained IGC scheme is proposed by combining the barrier Lyapunov function-based backstepping methodology and the specific output-based finite-time disturbance observer. Different from the existing methods, which require the state information and matched disturbances, the main features of the presented approach is capable of addressing the partial measurement knowledge and unmatched uncertainties simultaneously. The IGC model of hypersonic flight vehicles is first formulated, and based on that, the specific output-based finite-time disturbance observer (OFTDO) is proposed to achieve the finite-time estimation of the unmatched uncertainties through the output. Then, the constrained IGC strategy is constructed via the backstepping technique. The stability of the closed-loop system including the estimation and tracking errors dynamics is analyzed in detail. The effectiveness of the proposed method is verified by numerical simulations and Monte-Carlo tests. Full article
(This article belongs to the Special Issue Learning-Based Intelligent Control in Aerospace Applications)
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27 pages, 2891 KiB  
Article
A Generic Framework for Prognostics of Complex Systems
by Marie Bieber and Wim J. C. Verhagen
Aerospace 2022, 9(12), 839; https://doi.org/10.3390/aerospace9120839 - 16 Dec 2022
Cited by 2 | Viewed by 2037
Abstract
In recent years, there has been an enormous increase in the amount of research in the field of prognostics and predictive maintenance for mechanical and electrical systems. Most of the existing approaches are tailored to one specific system. They do not provide a [...] Read more.
In recent years, there has been an enormous increase in the amount of research in the field of prognostics and predictive maintenance for mechanical and electrical systems. Most of the existing approaches are tailored to one specific system. They do not provide a high degree of flexibility and often cannot be adaptively used on different systems. This can lead to years of research, knowledge, and expertise being put in the implementation of prognostics models without the capacity to estimate the remaining useful life of systems, either because of lack of data or data quality or simply because failure behaviour cannot be captured by data-driven models. To overcome this, in this paper we present an adaptive prognostic framework which can be applied to different systems while providing a way to assess whether or not it makes sense to put more time into the development of prognostic models for a system. The framework incorporates steps necessary for prognostics, including data pre-processing, feature extraction and machine learning algorithms for remaining useful life estimation. The framework is applied to two systems: a simulated turbofan engine dataset and an aircraft cooling unit dataset. The results show that the obtained accuracy of the remaining useful life estimates are comparable to what has been achieved in literature and highlight considerations for suitability assessment of systems data towards prognostics. Full article
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24 pages, 10465 KiB  
Article
Numerical Simulations of Spray Combustion in Jet Engines
by Arvid Åkerblom, Francesco Pignatelli and Christer Fureby
Aerospace 2022, 9(12), 838; https://doi.org/10.3390/aerospace9120838 - 16 Dec 2022
Cited by 5 | Viewed by 3758
Abstract
The aviation sector is facing a massive change in terms of replacing the currently used fossil jet fuels (Jet A, JP5, etc.) with non-fossil jet fuels from sustainable feedstocks. This involves several challenges and, among them, we have the fundamental issue of current [...] Read more.
The aviation sector is facing a massive change in terms of replacing the currently used fossil jet fuels (Jet A, JP5, etc.) with non-fossil jet fuels from sustainable feedstocks. This involves several challenges and, among them, we have the fundamental issue of current jet engines being developed for the existing fossil jet fuels. To facilitate such a transformation, we need to investigate the sensitivity of jet engines to other fuels, having a wider range of thermophysical specifications. The combustion process is particularly important and difficult to characterize with respect to fuel characteristics. In this study, we examine premixed and pre-vaporized combustion of dodecane, Jet A, and a synthetic test fuel, C1, based on the alcohol-to-jet (ATJ) certified pathway behind an equilateral bluff-body flameholder, spray combustion of Jet A and C1 in a laboratory combustor, and spray combustion of Jet A and C1 in a single-sector model of a helicopter engine by means of numerical simulations. A finite rate chemistry (FRC) large eddy simulation (LES) approach is adopted and used together with small comprehensive reaction mechanisms of around 300 reversible reactions. Comparison with experimental data is performed for the bluff-body flameholder and laboratory combustor configurations. Good agreement is generally observed, and small to marginal differences in combustion behavior are observed between the different fuels. Full article
(This article belongs to the Special Issue Large-Eddy Simulation Applications of Combustion Systems)
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20 pages, 5609 KiB  
Article
A Homogenization Method for Replacement Stator Models in an Aero-Engine
by Wenjun Wang, Yu Fan, Lin Li, Yuning Zhang and Zhiqiang Song
Aerospace 2022, 9(12), 837; https://doi.org/10.3390/aerospace9120837 - 16 Dec 2022
Cited by 1 | Viewed by 1490
Abstract
Generally, the high-fidelity finite element models of aero-engines comprise millions of degrees of freedom (DOFs). Although they can provide precise predictions of structural dynamics, the computational cost will be often unaffordable if appropriate dimension reduction techniques are not adopted. The homogenization of the [...] Read more.
Generally, the high-fidelity finite element models of aero-engines comprise millions of degrees of freedom (DOFs). Although they can provide precise predictions of structural dynamics, the computational cost will be often unaffordable if appropriate dimension reduction techniques are not adopted. The homogenization of the substructure, also termed as the physical replacement, reduces the model scale by simplifying the unnecessary details of the substructure, thus speeding up the dynamic analysis of the whole engine. In this study, we design the physical replacements for the stators of an aero-engine based on the long-wave assumption. These replacements have the same wave features as the stators in long-wave cases while possessing fewer DOFs. The core steps include the analytical description of the stators and the corresponding physical replacement design through two homogenizations. Specifically, we first investigate the wave characteristics of the stators using the wave finite element method and find two dominant waves: flexural and flexural–torsional coupled waves. The first homogenization introduces two analytical Timoshenko beams to describe the two wave motions of the stators. These two analytical beams are subsequently solidified into physical replacements with I, box, and open cross-sections in the second homogenization. The mechanical and geometric parameters are identified through a combination of the static analysis and the genetic algorithm (GA). The search processes are of great efficiency, because all the descriptions are analytical. Results show that the relative errors of the natural frequencies between the pristine stators and the physical replacements associated with the nodal diameters 6–15 are less than 5%. Full article
(This article belongs to the Special Issue Structural Dynamics and Control)
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12 pages, 1587 KiB  
Article
Experimental Study of Suppressing the Thermoacoustic Instabilities in a Rijke Tube Using Microsecond Discharge Plasma
by Jiangge Deng, Ting Li, Jinkui Wang and Chicheng Gao
Aerospace 2022, 9(12), 836; https://doi.org/10.3390/aerospace9120836 - 16 Dec 2022
Cited by 3 | Viewed by 1768
Abstract
Thermoacoustic instabilities occur when heat release is coupled with pressure fluctuation, which may cause performance degradation of the combustor and serious structural damage. This study focued on an active control method using discharge plasma and showed experimentally that discharge plasma can make a [...] Read more.
Thermoacoustic instabilities occur when heat release is coupled with pressure fluctuation, which may cause performance degradation of the combustor and serious structural damage. This study focued on an active control method using discharge plasma and showed experimentally that discharge plasma can make a difference in controlling the thermoacoustic instabilities in a Rijke tube. A vertically placed Rijke tube thermoacoustic system using induction heating tungsten mesh as a heat source was built. The results show that the high repetition rate discharge can effectively suppress the thermoacoustic oscillations in the Rijke tube and that they will not re-occur for some time. Additionally, their effectiveness depended more on average power than energy per pulse. Combining the collected pressure, schlieren data, and theoretical analysis, it can be suggested that the plasma discharge could heat the inlet airflow, which could influence the heat exchange and then could break thermo-acoustic coupling, and its high-frequency pressure perturbation might increase the dissipation of the energy of sound. Full article
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17 pages, 6510 KiB  
Article
Study on the Leading Edge of a Hypersonic Vehicle Using the Aero-Thermoelastic Coupling Method
by Long Chen and Jian Xia
Aerospace 2022, 9(12), 835; https://doi.org/10.3390/aerospace9120835 - 15 Dec 2022
Cited by 1 | Viewed by 2274
Abstract
The characteristics of aero-thermoelastic coupling are important for the design of the leading edge in hypersonic vehicles. Herein, a fluid–structure interaction analysis is performed to study the leading edge of a hypersonic vehicle using aero-thermoelastic coupling methods. The results show that the maximum [...] Read more.
The characteristics of aero-thermoelastic coupling are important for the design of the leading edge in hypersonic vehicles. Herein, a fluid–structure interaction analysis is performed to study the leading edge of a hypersonic vehicle using aero-thermoelastic coupling methods. The results show that the maximum heat flux and temperature of the optimized Bézier curve leading edge are reduced to a certain extent, compared with a hemi-cylindrical leading edge, and the lift–to–drag ratios of the two models are close. The Bézier curve leading-edge model can reduce the blunt radius of the leading edge of the hypersonic vehicle and increase the aerodynamic performance without losing thermal performance. Full article
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17 pages, 5462 KiB  
Article
Atomization Characteristics of Special-Design Pneumatic Two-Fluid Nozzles for Helicopter Main Reducers: A Numerical and Experimental Investigation
by He Liu, Huiyun Cheng, Yu Dai and Xiang Zhu
Aerospace 2022, 9(12), 834; https://doi.org/10.3390/aerospace9120834 - 15 Dec 2022
Cited by 3 | Viewed by 2424
Abstract
Oil mist lubrication can be utilized as an emergency lubrication system in the main reducer of a helicopter. A special-design pneumatic two-fluid nozzle is the crucial system component for atomizing lubricant oil, so exploring the atomization characteristics of the nozzle has a significance [...] Read more.
Oil mist lubrication can be utilized as an emergency lubrication system in the main reducer of a helicopter. A special-design pneumatic two-fluid nozzle is the crucial system component for atomizing lubricant oil, so exploring the atomization characteristics of the nozzle has a significance on effectively improving oil mist lubrication performance. A CFD (computational fluid dynamics) model with a DPM (discrete phase model) technique and a specialized atomization test system were set up to both numerically and experimentally investigate the nozzle’s atomization characteristics. For the atomization properties of the nozzle, the impacts of air pressure, gas–liquid pressure ratio, lubricant oil flow rate, and lubricant oil property factors, including viscosity and surface tension, were investigated. Combining the experimental and the numerical findings reveals that an increasing air pressure and gas–liquid pressure ratio contribute to the atomization effect of the nozzle, especially the air pressure. In addition, a higher lubricant oil flow rate is slightly unfavorable for atomization, but a rise in viscosity and surface tension prevents the atomization of the lubrication oil. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))
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27 pages, 1701 KiB  
Article
A Recursive Approach for Magnetic Field Estimation in Spacecraft Magnetic Attitude Control
by Mohammed A. A. Desouky and Ossama Abdelkhalik
Aerospace 2022, 9(12), 833; https://doi.org/10.3390/aerospace9120833 - 15 Dec 2022
Cited by 2 | Viewed by 2052
Abstract
This paper is concerned with magnetic attitude control of spacecraft. The operation of the magnetic actuators is usually on a duty cycle; during the off times in this duty cycle the magnetometers are used to measure the magnetic field around the spacecraft. This [...] Read more.
This paper is concerned with magnetic attitude control of spacecraft. The operation of the magnetic actuators is usually on a duty cycle; during the off times in this duty cycle the magnetometers are used to measure the magnetic field around the spacecraft. This alternate operation of magnetic actuators and sensors avoids the noise effect on the magnetometers coming from the magnetic actuators. This alternate operation results in longer maneuver times. This paper presents an estimation approach for the magnetic field, as well as the spacecraft attitude, that increases the duty cycle of the magnetic rods while reducing the rate of collecting the magnetometer data. A modified Multiplicative Extended Kalman Filter (MEKF) is used in the proposed approach. A relatively simple and fast dynamic model is developed for use in the MEKF. Monte Carlo simulations presented in this paper show that the proposed approach results in less maneuver time, and less power consumption by the magnetic rods when compared to a standard magnetic control approach. The magnetic field estimation process is verified using data collected from the CASSIOPE spacecraft using its telemetry system and the results are presented. Full article
(This article belongs to the Special Issue Spacecraft Attitude Control Using Magnetic Actuators)
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30 pages, 8852 KiB  
Article
Dynamic Boundary Optimization of Free Route Airspace Sectors
by Lei Yang, Jue Huang, Qi Gao, Yi Zhou, Minghua Hu and Hua Xie
Aerospace 2022, 9(12), 832; https://doi.org/10.3390/aerospace9120832 - 15 Dec 2022
Cited by 4 | Viewed by 2386
Abstract
Free Route Airspace (FRA) permits users to freely plan routes between defined entry and exit waypoints with the possibility of routing via intermediate waypoints, which is beneficial to improve flight efficiency. Dynamic management of sectors is essential for the future promotion of full-time [...] Read more.
Free Route Airspace (FRA) permits users to freely plan routes between defined entry and exit waypoints with the possibility of routing via intermediate waypoints, which is beneficial to improve flight efficiency. Dynamic management of sectors is essential for the future promotion of full-time FRA applications. In this paper, considering the demand uncertainty at the pre-tactical level, we construct an FRA complexity indicator system and use the XGBoost algorithm to predict the ATC workload. A two-stage sector boundary optimization method is proposed, using Binary Space Partition (BSP) to generate sector boundaries and an A*-based heuristic algorithm to automatically tune them to conform to the operational structure and “direct to” characteristics of FRA. Finally, this paper verifies the effectiveness of the proposed method for balancing ATC workload in a pre-designed Lanzhou FRA in China. Full article
(This article belongs to the Collection Air Transportation—Operations and Management)
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12 pages, 3698 KiB  
Article
Experimental and Numerical Study on the Influence of Rubbing Force on Radial Crack Initiation in Labyrinth Seal Fins
by Yicheng Yang, Jiaqi Chang, Zhaoguo Mi and Weihua Yang
Aerospace 2022, 9(12), 831; https://doi.org/10.3390/aerospace9120831 - 15 Dec 2022
Cited by 1 | Viewed by 1861
Abstract
Radial cracks appear in the labyrinth seal fins of the shrouded turbine blade of an aero-engine during service. To clarify the influence rule of rubbing force on crack initiation, a high-speed rubbing test bench and a numerical calculation model are established, and the [...] Read more.
Radial cracks appear in the labyrinth seal fins of the shrouded turbine blade of an aero-engine during service. To clarify the influence rule of rubbing force on crack initiation, a high-speed rubbing test bench and a numerical calculation model are established, and the research is carried out through experiment and numerical calculation. It is found that cracks can be initiated when the rubbing force is greater than 20 N with a high rubbing temperature at high speed. It is verified by numerical calculation and shows that pure mechanical load will not cause crack initiation, while the thermal load is the main reason for the radial crack initiation of fins. With the increase of rubbing force, the time of crack initiation increases, and the number and length of cracks decrease. At high rubbing temperatures, rubbing force will lead to radial crack initiation, which mainly affects the position of crack initiation. Full article
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16 pages, 4355 KiB  
Article
Theoretical Model and Numerical Analysis of the Tip Leakage Vortex Variations of a Centrifugal Compressor
by Shuli Hong, Jun Chi, Xin Xiang and Weiyu Lu
Aerospace 2022, 9(12), 830; https://doi.org/10.3390/aerospace9120830 - 15 Dec 2022
Cited by 6 | Viewed by 1948
Abstract
A centrifugal compressor of a micro turbine generator system is investigated by the theoretical model and numerical analysis to explore the characteristics of the tip leakage vortex as the centrifugal compressor approaches stall. The numerical simulation results show the cross-sectional shape of the [...] Read more.
A centrifugal compressor of a micro turbine generator system is investigated by the theoretical model and numerical analysis to explore the characteristics of the tip leakage vortex as the centrifugal compressor approaches stall. The numerical simulation results show the cross-sectional shape of the tip leakage vortex is elliptical, and its long and short axes are gradually stretched as the compressor approaches stall. Moreover, the vortex trajectory is inclined to the pressure side of the adjacent blade. In addition, the Kirchhoff elliptical vortex model is introduced to analyze the flow passage constriction effect, the passage vortex squeezing effect, and the leakage flow translation effect. Results show that there is no upper limit for the flow passage constriction effect on the tip leakage vortex. Furthermore, relative to the original vortex, the minimum constriction effect depends on the axis ratio of the elliptical tip leakage vortex. The passage vortex has an expansion effect on the tip leakage vortex rather than a squeezing effect, which is limited and also depends on the axis ratio of the ellipse. However, the effect magnitude of the leakage flow depends on the scales both of the long and short axes, which also have no upper limit. Full article
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20 pages, 8723 KiB  
Article
Image Quality Enhancement with Applications to Unmanned Aerial Vehicle Obstacle Detection
by Zhaoyang Wang, Dan Zhao and Yunfeng Cao
Aerospace 2022, 9(12), 829; https://doi.org/10.3390/aerospace9120829 - 15 Dec 2022
Cited by 1 | Viewed by 1959
Abstract
Aiming at the problem that obstacle avoidance of unmanned aerial vehicles (UAVs) cannot effectively detect obstacles under low illumination, this research proposes an enhancement algorithm for low-light airborne images, which is based on the camera response model and Retinex theory. Firstly, the mathematical [...] Read more.
Aiming at the problem that obstacle avoidance of unmanned aerial vehicles (UAVs) cannot effectively detect obstacles under low illumination, this research proposes an enhancement algorithm for low-light airborne images, which is based on the camera response model and Retinex theory. Firstly, the mathematical model of low-illumination image enhancement is established, and the relationship between the camera response function (CRF) and brightness transfer function (BTF) is constructed by a common parameter equation. Secondly, to solve the problem that the enhancement algorithm using the camera response model will lead to blurred image details, Retinex theory is introduced into the camera response model to design an enhancement algorithm framework suitable for UAV obstacle avoidance. Thirdly, to shorten the time consumption of the algorithm, an acceleration solver is adopted to calculate the illumination map, and the exposure matrix is further calculated via the illumination map. Additionally, the maximum exposure value is set for low signal-to-noise ratio (SNR) pixels to suppress noise. Finally, a camera response model and exposure matrix are used to adjust the low-light image to obtain an enhanced image. The enhancement experiment for the constructed dataset shows that the proposed algorithm can significantly enhance the brightness of low-illumination images, and is superior to other similar available algorithms in quantitative evaluation metrics. Compared with the illumination enhancement algorithm based on infrared and visible image fusion, the proposed algorithm can achieve illumination enhancement without introducing additional airborne sensors. The obstacle object detection experiment shows that the proposed algorithm can increase the AP (average precision) value by 0.556. Full article
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19 pages, 2465 KiB  
Article
A Two-Phase Mass Flow Rate Model for Nitrous Oxide Based on Void Fraction
by Simone La Luna, Nicola Foletti, Luca Magni, Davide Zuin and Filippo Maggi
Aerospace 2022, 9(12), 828; https://doi.org/10.3390/aerospace9120828 - 15 Dec 2022
Cited by 3 | Viewed by 4122
Abstract
In the field of space propulsion, self pressurized technology is an example of innovation capable of improving system performances through reduction of volumes and other optimizations. Potential applications are widespread and not limited to the propulsion panorama: from on-orbit maneuvering to in-orbit servicing, [...] Read more.
In the field of space propulsion, self pressurized technology is an example of innovation capable of improving system performances through reduction of volumes and other optimizations. Potential applications are widespread and not limited to the propulsion panorama: from on-orbit maneuvering to in-orbit servicing, from refueling of satellites at the end of life to in situ resource exploitation for missions headed towards remote objects of the solar system. However, important drawbacks have been reported for these systems: modeling of fluids and thermal phenomena is complex, thus preventing accurate performance predictions. As a result, no comprehensive and accurate model capable of describing the dynamics of a self-pressurizing propellant tank has been developed so far. In this context, this paper proposes a two-phase mass flow rate model based on void fraction. N2O has been selected due to its use as a green and self-pressurized propellant for in-space propulsive applications. The aim of this paper is to describe the current mass flow rate models present in the literature for this fluid and compare the new model with the one proposed by Dyer. A model validation is also offered, and a test campaign is mentioned. Finally, preliminary results are shown and discussed: results are then compared with the ones obtained through the Dyer model, in order to retrieve a comprehensive comparison among the two simulation frameworks. Comments on the results are added, showing the improvements as well as the limitations of the proposed framework. Full article
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23 pages, 3588 KiB  
Review
Progress of Porous/Lattice Structures Applied in Thermal Management Technology of Aerospace Applications
by Jian Liu, Mengyao Xu, Rongdi Zhang, Xirui Zhang and Wenxiong Xi
Aerospace 2022, 9(12), 827; https://doi.org/10.3390/aerospace9120827 - 15 Dec 2022
Cited by 22 | Viewed by 5033
Abstract
With lightweight, multifunctional, and designable characteristics, porous/lattice structures have started to be used in aerospace applications. Porous/lattice structures applied in the thermal management technology of aerospace vehicles have attracted much attention. In the past few years, many related numerical and experimental investigations on [...] Read more.
With lightweight, multifunctional, and designable characteristics, porous/lattice structures have started to be used in aerospace applications. Porous/lattice structures applied in the thermal management technology of aerospace vehicles have attracted much attention. In the past few years, many related numerical and experimental investigations on flow, heat transfer, modelling methodology, and manufacturing technology of porous/lattice structures applied in thermal management systems have been widely conducted. This paper lists the investigations and applications of porous/lattice structures applied in thermal management technology from two aspects, i.e., heat transfer enhancement by porous/lattice structures and transpiration cooling. In addition, future developments and challenges based on the previous investigations are analyzed and summarized. With the higher requirements of thermal protection for aerospace applications in the future, thermal management technology based on porous/lattice structures shows good prospects. Full article
(This article belongs to the Special Issue Heat Transfer, Combustion and Flow Dynamics in Propulsion Systems)
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11 pages, 3721 KiB  
Article
Supersonic Combustion Mode Analysis of a Cavity Based Scramjet
by Yu Meng, Wenming Sun, Hongbin Gu, Fang Chen and Ruixu Zhou
Aerospace 2022, 9(12), 826; https://doi.org/10.3390/aerospace9120826 - 15 Dec 2022
Cited by 6 | Viewed by 2411
Abstract
Since flame stability is the key to the performance of scramjets, scramjet combustion mode and instability characteristics were investigated by using the POD method based on a cavity-stabilized scramjet. Experiments were developed on a directly connected scramjet model that had an inlet flow [...] Read more.
Since flame stability is the key to the performance of scramjets, scramjet combustion mode and instability characteristics were investigated by using the POD method based on a cavity-stabilized scramjet. Experiments were developed on a directly connected scramjet model that had an inlet flow of Mach 2.5 with a cavity stabilizer. CH* chemiluminescence, schlieren, and a wall static pressure sensor were employed to observe flow and combustion behavior. Three typical combustion modes were classified by distinguishing averaged CH* chemiluminescence images of three ethylene fuel jet equivalence ratios. The formation reason was explained using schlieren images and pressure characteristics. POD modes (PDMs) were determined using the proper orthogonal decomposition (POD) of sequential flame CH* chemiluminescence images. The PSD (power spectral density) of the PDM spectra showed large peaks in a frequency range of 100–600 Hz for three typical stabilized combustion modes. The results provide oscillation characteristics of three scramjet combustion modes. Full article
(This article belongs to the Special Issue Advances in Hypersonic Aircraft Propulsion Technology)
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18 pages, 2929 KiB  
Article
Blade-Tip Vortex Noise Mitigation Traded-Off against Aerodynamic Design for Propellers of Future Electric Aircraft
by Hua-Dong Yao, Zhongjie Huang, Lars Davidson, Jiqiang Niu and Zheng-Wei Chen
Aerospace 2022, 9(12), 825; https://doi.org/10.3390/aerospace9120825 - 15 Dec 2022
Cited by 4 | Viewed by 13326
Abstract
We study noise generation at the blade tips of propellers designed for future electric aircraft propulsion and, furthermore, analyze the interrelationship between noise mitigation and aerodynamics improvement in terms of propeller geometric designs. Classical propellers with three or six blades and a conceptual [...] Read more.
We study noise generation at the blade tips of propellers designed for future electric aircraft propulsion and, furthermore, analyze the interrelationship between noise mitigation and aerodynamics improvement in terms of propeller geometric designs. Classical propellers with three or six blades and a conceptual propeller with three joined dual-blades are compared to understand the effects of blade tip vortices on the noise generation and aerodynamics. The dual blade of the conceptual propeller is constructed by joining the tips of two sub-blades. These propellers are designed to operate under the same freestream flow conditions and similar electric power consumption. The Improved Delayed Detached Eddy Simulation (IDDES) is adopted for the flow simulation to identify high-resolution time-dependent noise sources around the blade tips. The acoustic computations use a time-domain method based on the convective Ffowcs Williams–Hawkings (FW-H) equation. The thrust of the 3-blade conceptual propeller is 4% larger than the 3-blade classical propeller and 8% more than the 6-blade one, given that they have similar efficiencies. Blade tip vortices are found emitting broadband noise. Since the classical and conceptual 3-blade propellers have different geometries, especially at the blade tips, they introduce deviations in the vortex development. However, the differences are small regarding the broadband noise generation. As compared to the 6-blade classical propeller, both 3-blade propellers produce much larger noise. The reason is that the increased number of blades leads to the reduced strength of tip vortices. The findings indicate that the noise mitigation through the modification of the blade design and number can be traded-off by the changed aerodynamic performance. Full article
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25 pages, 17593 KiB  
Article
Aerodynamic Response of a Serpentine Inlet to Horizontal Periodic Gusts
by Shu Sun, Zhenlong Wu, Hexia Huang, Galih Bangga and Huijun Tan
Aerospace 2022, 9(12), 824; https://doi.org/10.3390/aerospace9120824 - 14 Dec 2022
Cited by 8 | Viewed by 2136
Abstract
Gust is a common atmospheric turbulence phenomenon encountered by aircraft and is one major cause of several undesired instability problems. Although the response of aircraft to the incoming gust has been widely investigated within the subject of external-flow aerodynamics in the past decades, [...] Read more.
Gust is a common atmospheric turbulence phenomenon encountered by aircraft and is one major cause of several undesired instability problems. Although the response of aircraft to the incoming gust has been widely investigated within the subject of external-flow aerodynamics in the past decades, little attention is paid to its effects on the internal flow within aircraft engines. In this paper, a newly implemented Field Velocity Method (FVM) in OpenFOAM is used to simulate the flow field and aerodynamic responses of a serpentine inlet exposed to non-stationary horizontal sinusoidal gusts. Validations are performed on the results obtained based on the baseline Computational Fluid Dynamics (CFD) solver and the gust modeling method. Finally, the flow field and aerodynamic characteristics of the serpentine inlet under horizontal sinusoidal gust conditions are comprehensively investigated. It is found that the gusts not only significantly change the flow structure but also play an unfavorable role in the total pressure distortion of the serpentine inlet. This finding shows the necessity to consider gust effects when designing and evaluating the performance of aircraft engines. Full article
(This article belongs to the Special Issue Thermal Fluid Dynamics and Control in Aerospace)
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22 pages, 1808 KiB  
Article
An Approach to the Preliminary Sizing and Performance Assessment of Spaceplanes’ Landing Parafoils
by Jasmine Rimani, Nicole Viola and Antonio Saluzzi
Aerospace 2022, 9(12), 823; https://doi.org/10.3390/aerospace9120823 - 14 Dec 2022
Cited by 4 | Viewed by 2151
Abstract
In this new era of space exploration, reusability and lower environmental impact are critical drivers in pursuing innovative solutions for access to space. One of these leading solutions is the Space Rider, a European reusable space plane with the ability to be both [...] Read more.
In this new era of space exploration, reusability and lower environmental impact are critical drivers in pursuing innovative solutions for access to space. One of these leading solutions is the Space Rider, a European reusable space plane with the ability to be both an “access to space” and a “return from space”. Following the lesson learned from the Intermediate eXperimental Vehicle (IXV) design and testing, the Space Rider will be equipped with a parafoil to enhance manoeuvrability during landing. Politecnico di Torino (PoliTO), in collaboration with Thales Alenia Space Italy (TAS-I), has developed an integrated tool to assess the landing performances of spaceplanes equipped with parafoils during conceptual design. The presented approach fuses sizing, dynamic models, guidance and control algorithms to provide a software suite for the rapid prototyping, sizing and performance assessment of spaceplanes’ parafoils. This paper details the implementation, mathematical background, validation and lessons learned behind the different software modules. Full article
(This article belongs to the Special Issue Aerospace System Design)
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32 pages, 5476 KiB  
Article
Helicopter Rescue for Flood Disaster: Scheduling, Simulation, and Evaluation
by Yuanbo Xue, Yuan Gao, Yongliang Tian, Hu Liu and Xiyu Wang
Aerospace 2022, 9(12), 822; https://doi.org/10.3390/aerospace9120822 - 14 Dec 2022
Cited by 2 | Viewed by 3795
Abstract
Frequent severe floods have caused great losses to urban safety and the economy, which raises high requirements for the efficiency and effectiveness of emergency rescue. Due to the flood characteristics, flood rescue requires a more rapid responder and decision-making compared with other kinds [...] Read more.
Frequent severe floods have caused great losses to urban safety and the economy, which raises high requirements for the efficiency and effectiveness of emergency rescue. Due to the flood characteristics, flood rescue requires a more rapid responder and decision-making compared with other kinds of disaster rescue. In recent years, aviation emergency rescue (AER) has attracted much attention for flood applications. In order to evaluate the effectiveness of AER for flood disasters, the present study proposes a conceptual model of helicopter AER scheduling and develops a simulation system of helicopter AER scheduling using multiple agents. Seven elements are considered in the conceptual model: helicopters, the command-and-control center, temporary take-off/landing points, mission demand points, resettlement points, loading points, and unloading points. Furthermore, process-oriented and object-oriented scheduling rules are developed as the general guide for scheduling. In order to efficiently simulate and evaluate an AER mission (assisting the decision maker), the simulation system is designed with multiple agents and a user interface, which can quickly load mission settings, run the simulation, and collect data for further evaluation. A standardized mission makespan is adopted as the evaluation index. Based on that, the minimum integrated index can be derived to finally assess the different rescue schemes and choose the best. In the case study, the comparison results indicate that the rescue efficiency of large helicopters (Mi-26 in the case) could be limited by the capabilities of loading points and unloading points. This problem is solved by scheduling small/medium-size helicopters to transfer the personnel. Alternately, two types of helicopters can be used: one for passenger transfer and the other for goods/material transfer. Anyway, the analyses in the case study illustrate the correlation between effectiveness and scheduling, which demonstrates the significance of decision-making. By using the proposed scheduling and modeling methods, the simulation system can be served as a convenient decision-making support tool for practical rescue applications. Full article
(This article belongs to the Collection Air Transportation—Operations and Management)
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13 pages, 1929 KiB  
Article
Influence of the Measurements Uncertainties in the Correlation of Spacecraft Thermal Models against Thermal Results
by Iñaki Garmendia and Eva Anglada
Aerospace 2022, 9(12), 821; https://doi.org/10.3390/aerospace9120821 - 14 Dec 2022
Viewed by 1809
Abstract
Ground thermal tests are always mandatory before any space mission is flown into space. The collected results of these tests are mainly temperatures of the different parts of the spacecraft (nodes) for different mission scenarios. The measured temperatures always show differences with the [...] Read more.
Ground thermal tests are always mandatory before any space mission is flown into space. The collected results of these tests are mainly temperatures of the different parts of the spacecraft (nodes) for different mission scenarios. The measured temperatures always show differences with the expected values coming from the computer thermal mathematical models. The origin of these differences is partially related to the inherent error coming from physical measurements. The thermal parameters that compose the computer thermal mathematical models must always be correlated with the results coming from tests. This paper studies, through three thermal models, the difficulties that are found in the correlation process when the measured temperatures reach a certain level of error. Thermal parameters become more difficult to be identified when the measurement error level increases. However, the temperature fields obtained with these poor thermal parameters are good enough for the mission thermal analysis. Several error levels, different load cases and correlation for steady-state and transient cases are studied to probe these findings. Full article
(This article belongs to the Section Astronautics & Space Science)
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